Department of Crop Sciences University of Illinois at Urbana-Champaign

Agronomy Day 2006

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Adding to the quality of life through flowers selected for shady landscapes and sustainable production

Daniel Warnock Daniel Warnock and Kevin Collins
Associate Professor, Floriculture Production and Research Assistant
Department of Natural Resources and Environmental Science

In 1998, the floriculture breeding program was initiated at UIUC with commercial impatiens germplasm and Costa Rican populations. Over the next several years evaluation techniques to identify host plant resistance to western flower thrips, a significant insect pest, were developed and refined. Greenhouse-based evaluations combine insect preference for individual plants and isolation cages to minimize false positives (“resistant” plants).

Impatiens are an outcrossing species with pollen shed and stigma receptivity separated by one or two days. To obtain inbred lines, pollen collected from a single plant is manually transferred to other flowers on the same plant. Seed pods develop over the next two to three weeks.

figure 1

Large phenotype impatiens selected in 2005 (metal reference stick is 48” long). Progeny from this selection are in the 2006 trials.

Seed dispersal in nature is through a rapid and explosive rupturing of mature seed pods. To protect against seed loss, individual seed pods are covered with gauze finger bandages such that seed are captured upon pod rupture. Inbreeding depression, expressed as reduced pollen production and viability, quickly appears after several generations of self pollinations. Male sterility exists in many commercial cultivars and appears to be linked to insect resistance making impatiens a challenging crop with which to work.

As a result of the evaluation procedures developed at UIUC and selection for good pollen shed, several impatiens populations with improved levels of resistance to western flower thrips were developed. These are the only know impatiens with resistance to feeding by western flower thrips. Through breeding and selection, the resistance ratings in improved populations have shifted from a mean of 6.1 in the original Costa Rican populations to 3.8 in the most resistant 2005 population. The rating scale is 1 to 9 with 1 = no damage and 9 =>35 leaves damaged by thrips. The impatiens populations and subsequently developed inbred lines with improved resistance have tremendous potential for reducing the amount of pesticides used in commercial greenhouses but the improved impatiens are not acceptable for many phenotypic traits.

Trials to identify novel phenotypic traits and to improve commercialization of thrips-resistant impatiens were initiated in 2003 and expanded in 2005 to include more than 4000 seedlings. The objectives of the phenotypic trials are to select for novel impatiens flower colors or patterns, floriferous plants with large or small flowers, dark green, silver, or varigated leaves, large upright or spreading plants, and highly branched plants. The entries in this year’s trial mainly are segregating populations from which individual plants with desirable characteristics will be selected to develop inbred lines. Commercial cultivars, designated by “CC” before the entry number, are interspersed throughout the trialing area as phenotypic controls.

Entries in the eastern section of the shade structure were all derived from large upright phenotypes. We expect to identify individual plants with superior branching, higher flower number, and larger flower size in these entries. Entries numbered 57, 58, and 59 were derived from parents with a bright orange eye in each flower. We expect to identify individual plants with larger eyes, more vibrant orange pigmentation, large flowers, and good branching habit in these entries. The entries numbered 54, 55, and 56 were derived from parents with an intensely colored border. This novel flower type is available commercially and we expect to select for novel color combinations with the petoy border. Entry number 60 was derived from Costa Rican parents with a unique spotting on flower petals. This phenotype is unstable across environments and at present is commercially unavailable. We expect to select for improved spotting, color intensity, and larger flowers in this entry.

We would like to thank the following for their support.